Anti-epidermal growth factor receptor antibodies and uses thereof

ABSTRACT

The present invention discloses humanized anti-epidermal growth factor receptor antibodies, which have favorable binding activity (the binding affinity being 6.13×10 −10  mol/L) and are able to inhibit the growth and migration of tumor cells. The present invention also discloses the preparation methods and uses of the antibodies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/CN2009/001605, filed Dec. 30, 2009, whichwas published in a non-English language, which claims priority to CN200910237804.2, filed Nov. 11, 2009.

FIELD OF THE INVENTION

The present invention relates to an antibody against epidemic growthfactor receptors as well as encoding genes thereof and uses of the same.

DESCRIPTION OF BACKGROUND

The epidemic growth factor receptor (EGFR) is a member of the family ofepidemic growth factor genes (erbB), which is overexpressed in about 30%of human tumors, especially non-small cell lung carcinomas, head andneck squamous cell carcinomas, colorectal carcinomas and the like. Manystudies indicate that antibodies against EGFR may effectively inhibitEGFR signal transduction pathway by blocking the binding of ligandsextracellularly, which showed promising therapeutic effect on multipleEGFR overexpressing or mutated human tumors, especially head and necksquamous cell carcinomas (80%˜100%), colorectal cancer (25%˜77%),non-small cell lung cancer (40%˜80%) and the like. Epidemic growthfactor receptor is one of the current therapeutic targets for tumor thatare intensively investigated and well-focused at present. Utilizinggenetic engineering in developing an anti-EGFR monoclonal antibodybecomes one of research hotspots for immunotherapy of tumor.

In 2004 and 2006, the U.S. Food and Drug Administration had successivelyapproved a murine-human chimeric antibody cetuximab and a full humanantibody panitumumab against EGFR for treatment of colorectalcarcinomas; in 2005, a humanized antibody nimotuzumab against EGFR wasawarded new drug certificate by Chinese State Food and DrugAdministration (SFDA), its Phase II/III clinical trial is under way. Useof murine monoclonal antibody in human bodies may induce humananti-murine antibody reaction, and thereby affecting its functionsthereof. Application of genetic engineered murine-human chimericantibody can greatly reduce the immunogenicity of the murine monoclonalantibody, prolong the half life of the antibody in bodies, and furtherenhance the biological effect of the antibody by virtue of the Fc regionof human immunoglobulin mediated immunomodulation and ADCC effect;however, the ability of this chimeric antibody to bind to an antigen islower than that of the murine antibody by 98.7%. A large number ofpre-clinical trials and clinical trials each has proven that cetuximab,alone and in combination with chemotherapy/radiotherapy, has a bettertherapeutic effect, but simple CDR transplant tends to cause drop inantigen-antibody affinity; panitumumab is a full human antibody preparedwith transgenic mice technology, which, comparing with the chimericantibody and humanized antibody, has a human sequence of near 100%,greatly increasing the antibody-target affinity, but this antibody hassuch defects as glycosylation pattern of murine, short half life, morehypersensitivity reactions and the like. Nimotuzumab gives a humanizedantibody through humanized remodeling of the anti EGFR murine monoclonalantibody, which links the light and heavy chains of the antibodyrespectively to different expression vectors for expression; since theexpressions of the light and heavy chains are quite different, themolecular expression level of the complete antibody tends to be verylow.

DISCLOSURE OF THE INVENTION

One of the purposes of the present invention is to provide an antibodythat may bind to epidemic growth factor receptor (EGFR).

The present invention provides an antibody, its variable region of heavychain has an amino acid sequence as set forth by SEQ ID NO. 3 in thesequence listing, and its light chain has an amino acid sequence as setforth by SEQ ID NO. 2 in the sequence listing.

The antibody may be composed of a heavy chain and the light chain, andthe heavy chain is composed of the heavy chain variable region and aheavy chain constant region.

The heavy chain constant region has an amino acid sequence as set forthby SEQ ID NO. 11 in the sequence listing.

The encoding gene of the above heavy chain variable region or theencoding gene of the above light chain also belong to the protectionscope of the present invention.

Encoding gene of the heavy chain variable region is set forth by thefollowing 1), 2) or 3):

1) a DNA molecule having a nucleotide sequence as set forth by SEQ IDNO. 6 in the sequence listing;

2) a DNA molecule, which hybridizes with the DNA sequence defined in 1)under stringency conditions, and which encodes the heavy chain variableregion;

3) a DNA molecule encoding the heavy chain variable region,characterized in that amino acid sequence encoding the heavy chainvariable region contains sequence having more than 70% homologous toamino acids at positions 51-70 starting from the N-terminal of SEQ IDNO. 3 in the sequence listing (i.e., nucleotides at positions 153 bp-210bp starting from the 5′ end of SEQ ID NO. 6 in the sequence listing);

Encoding gene of the light chain is set forth by the following I), II)or III):

I) a DNA molecule having a nucleotide sequence as set forth by SEQ IDNO. 5 in the sequence listing;

II) a DNA molecule, which hybridizes with the DNA sequence defined in I)under stringency conditions, and which encodes the light chain;

III) a DNA molecule encoding the light chain, characterized in thatamino acid sequence encoding the light chain contains sequence havingmore than 70% homologous to amino acids at positions 24-34 starting fromthe N-terminal of SEQ ID NO. 2 in the sequence listing (i.e.,nucleotides at positions 72 bp-102 bp starting from the 5′ end of SEQ IDNO. 5 in the sequence listing);

Encoding gene of the heavy chain constant region is set forth by thefollowing a) or b):

a) a DNA molecule having a nucleotide sequence as set forth by SEQ IDNO. 12 in the sequence listing;

b) a DNA molecule having a nucleotide sequence as set forth by SEQ IDNO. 13 in the sequence listing.

A primer pair used for amplifying full-length of any of the aboveencoding genes or any fragment thereof also belongs to the protectionscope of the present invention.

The primer pairs are the following primer pairs: the following primerpairs are used for amplifying the light chain encoding genes.

1) one primer sequence is set forth by SEQ ID NO. 7 in the sequencelisting, and the other primer sequence of the primer pair is set forthby SEQ ID NO. 8 in the sequence listing;

2) one primer sequence is set forth by SEQ ID NO. 9 in the sequencelisting, and the other primer sequence of the primer pair is set forthby SEQ ID NO. 10 in the sequence listing.

A recombinant vector, a recombinant strain, a transgenic cell line or anexpression cassette containing any of the above encoding genes alsobelongs to the protection scope of the present invention.

Another purpose of the present invention is to provide a method forpreparing the above antibody.

The method for preparing the above antibody provided by the presentinvention comprising introducing any of the above encoding genes into ahost cell and cultivating to give said antibody.

In the method, any of the above encoding genes may be introduced intothe host cell via a recombinant vector; the recombinant vector containsboth any of the above encoding genes of the heavy chain variable regionand any of the above encoding genes of the light chain, and the encodinggene of the heavy chain variable region and the encoding gene of thelight chain are regulated by the same promoter in the recombinantvector.

Another purpose of the present invention is to provide an inhibitor forinhibiting the signal transduction pathway of the epidemic growth factorreceptor, an inhibitor for inhibiting a tumor cell invasion or a drugfor preventing and/or treating a tumor.

The active ingredient of the drug or the inhibitor provided by thepresent invention is any of the above antibody and/or any of theencoding genes.

Particularly, with regard to the above drug or inhibitor, the tumor maybe a colon cancer; and the tumor cell may be a SW480 cell.

Use of the above antibody and/or any of the encoding genes in preparingan inhibitor for inhibiting the signal transduction pathway of theepidemic growth factor receptor also belongs to the protection scope ofthe present invention.

Use of the above antibody and/or any of the encoding genes in preparingan inhibitor for inhibiting a tumor cell invasion also belongs to theprotection scope of the present invention.

Use of the above antibody and/or any of the encoding genes in preparinga drug for preventing and/or treating a tumor also belongs to theprotection scope of the present invention.

Use of the above antibody and/or any of the encoding genes in inhibitingthe signal transduction pathway of the epidemic growth factor receptoralso belongs to the protection scope of the present invention.

Use of the above antibody and/or any of the encoding genes in inhibitinga tumor cell invasion also belongs to the protection scope of thepresent invention.

Use of the above antibody and/or any of the encoding genes in preventingand/or treating a tumor also belongs to the protection scope of thepresent invention.

Particularly, in the above uses, the tumor may be a colon cancer; andthe tumor cell may be a SW480 cell.

Based on the establishment of the antibody-antigen crystal structure,and by means of computer simulation, the present invention subjected thesurface gene from the murine variable region FR of the cetuximabantibody to mutation, making it to be similar with the human antibody FRin form, thereby obtaining an anti-EGFR humanized antibody withsignificantly improved affinity comparing with that of the cetuximab.The experimental results demonstrate that the antibody of the presentinvention has a good binding activity (with an affinity of 6.13×10⁻¹⁰ M)and an ability of inhibiting tumor cell growth and migration; however,the anti-EGFR human-murine chimeric antibody, cetuximab, commonly foundin foreign market has an affinity of 1.1×10⁻⁹ M. The humanized antibodyof the present invention is capable of better binding with EGFR, thusguaranteeing the anti-tumor effect thereof. The present method forpreparing an antibody enables the light chain and the heavy chain to beexpressed simultaneously, such that the expression ratio of the lightchain to the heavy chain gets closer to 1:1, producing a higher ratio ofmatching double strand antibodies. In summary, the antibody andpreparation method thereof of the present invention will have a broadapplication prospect in the field in preventing and/or treating a tumor.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B, an agarose gel electrophoresis of the PCR amplificationproducts of the light chain gene (FIG. 1A) and the heavy chain variableregion gene (FIG. 1B).

FIG. 2, a structural schematic view of an expression vector containingthe antibody of the present invention.

FIG. 3, a reduced SDS-PAGE assay of the antibody of the presentinvention.

FIG. 4, an immunobiological imprinting analysis of the antibody of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The experimental method used in the following Examples each is aconventional method unless otherwise indicated.

The materials, reagents and the like used in the following Examples eachis commercially available unless otherwise indicated.

EXAMPLE 1 Obtaining of the Encoding Genes for the Light Chain and theHeavy Chain Variable Region of the Antibody

Based on computer simulation, and with the amino acid sequence of themurine-human chimeric antibody, cetuximab, as a template, the surfacegene of the murine FR was subjected to humanized remodeling, such thatthe amino acid sequence of the light chain L2 and the amino acidsequence of the heavy chain variable region H1 were designed andsynthesized;

The light chain L1: the amino acid sequence is set forth by SEQ ID NO. 1in the sequence listing; the sequence of the encoding gene is set forthby SEQ ID NO. 4 in the sequence listing;

The light chain L2: the amino acid sequence is set forth by SEQ ID NO. 2in the sequence listing; the sequence of the encoding gene is set forthby SEQ ID NO. 5 in the sequence listing;

The heavy chain variable region H1: the amino acid sequence is set forthby SEQ ID NO. 3 in the sequence listing; the sequence of the encodinggene is set forth by SEQ ID NO. 6 in the sequence listing;

The antibody of the present invention, referred to as C3, is composed ofthe light chain L2 and the heavy chain variable region H1.

The encoding gene of the light chain L1 and the encoding gene of theheavy chain variable region H2 were produced by artificialsynthesization.

The encoding gene of the light chain L2: an overlap PCR method wasperformed, wherein the encoding gene of the light chain L1 was used as atemplate to perform amplification with primers 1, 2, 3 and 4 so as togive the encoding gene of the light chain L2;

Primers:

1: (SEQ ID NO. 7) 5′-gtggctagcgccgccaccatggacat-3′; (Nhel) 2:(SEQ ID NO. 8) 5′-gaattcctaacactctccectgttga-3′; (EcoRl ) 3:(SEQ ID NO. 9) 5′-ggattcaataccctgacttgcccggcaggcaat-3 ′; 4:(SEQ ID NO. 10) 5′-attgcctgccgggcaagtcagggtattgaatccaacttacactggtatcagcagaaacca-3′;

Each of the amplified genes was detected by gel electrophoresis, and theresult was consistent with the expected size, L and H has a fragmentsize of about 735 bp and 770 bp, respectively (FIG. 1). M: relativemolecular mass standard; A: lane 1, light chain gene product L1, lane 2,light chain gene product L2; B: lane 1, heavy chain variable region geneproduct H1.

The encoding gene of the light chain L2 and the encoding gene of theheavy chain variable region H1 were separately cloned into the pMD18-Tvector (recorded as the recombinant vectors pMD18-T/L2 and pMD18-T/H1,respectively), transformed into Escherichia coli DH5α, and then, cloneswere picked and, from which plasmids were extracted and identified bysequencing. The results indicated that each of the obtained genesequences is correct.

EXAMPLE 2 Preparation of the Antibody

I. Construction of the Recombinant Expression Vector:

The pIRES dual expression vector, Cat. No.: 631605, was purchased fromClontech company; the pMD18-T expression vector, Cat. No.: D504 CA, waspurchased from Takara Bio Company. The pIRES vector itself contains aheavy chain constant region gene. The heavy chain constant region has anamino acid sequence as set forth by SEQ ID NO. 11 in the sequencelisting, the encoding gene thereof has a genomic DNA sequence as setforth by SEQ ID NO. 12 in the sequence listing and a cDNA sequence asset forth by SEQ ID NO. 13 in the sequence listing. The heavy chainconstant region gene in the pIRES vector is the genomic gene as setforth by SEQ ID NO. 12.

The recombinant vector pMD18-T/L2 and pIRES dual expression vector wereseparately cleaved with corresponding restriction endonucleases (NheIand EcoRI), and then, the target fragments were recovered and purifiedafter gel electrophoresis; the light chain gene fragments L2 and thevector fragments were uniformly mixed, reacting at 16° C. for 12 h underaction of the ligation agent. The reaction products were transformedinto E. coli DH5α, and then, clones were picked and, from which plasmidswere extracted and identified by sequencing. The results showed thatboth the insertion direction and the insertion sequence of the gene arecorrect in the recombinant expression vector, recorded as therecombinant expression vector pIRES/L2.

pIRES/L2 was used as a template and cleaved enzymatically with Xba I andNot I, and then, the resulting large fragments were recovered andrecorded as fragment 1; pMD18-T/H1, cloned with the heavy chain variableregion gene, was used as a template and cleaved enzymatically with Xba Iand BamH I, and then, the heavy chain variable region fragments wererecovered and recorded as fragment 2; pIRES vector, cloned with theheavy chain constant region gene, was used as a template and cleavedenzymatically with BamH I and Not I, and then, the heavy chain constantregion fragments (the heavy chain constant region fragment resultingfrom cleavage with BamH I and Not I has a sequence as set forth by SEQID NO. 12) were recovered and recorded as fragment 3; fragments 1, 2 and3 were linked to give a recombinant vector, which was then transformedinto E. coli DH5α, after which clones were picked and, from whichplasmids were extracted and identified by sequencing. The results showthat structure of the resulting recombinant expression vector iscorrect, and the genes were inserted in correct direction and order; thelight chain gene and heavy chain gene of the antibody share a commonpromoter; an expression plasmid was finally constructed through ligationby IRES sequence. The recombinant expression vector was recorded aspIRES/L2/H1 (FIG. 2).

II. Cell Transformation and Protein Expression

293T cell (293T human embryonic kidney T cell), Cat. No.: CRL-11268, waspurchased from American Type Culture Collection (ATCC); Lipofectamine2000, Cat. No.: 12566014, was purchased from Invitrogen company;HyQSFM4CHO medium, Cat. No.: SH30518.02, was purchased from HyClonecompany; rProtein A chromatography column, Cat. No.: 17-5079-01, waspurchased from GE company.

293T cell was inoculated into a 10 cm-diameter petri dish at 1×10⁶/ml,and cultured in a DMEM medium containing 10% fetal bovine serum at a 5%CO₂ incubator at 37° C. 5 μg of the resulting plasmid pIRES/L2/H1obtained in step I was used to transfect 293T cell to give a recombinantcell 293T-pIRES/L2/H1, which was performed in accordance with thereagent instruction of Lipofectamine 2000.

The recombinant cell 293T-pIRES/L2/H1 was cultivated in a serum-freeDMEM medium for 6˜8 h prior to sucking out the serum-free medium andreplacing with a HyQSFM4CHO medium. Then, co-cultivation continued to beconducted under the same condition for 84 h, and cell supernatant wascollected at an interval of 12 h and primarily detected with the ELISAmethod for the expression of the antibody. Scaling-up the transfectionsystem, cell cultivation supernatant of 4.5 L was collected and adjustedto pH 6.0˜7.0 and filtered through a 0.45 μm filter film, and theantibody was then purified by the rProtein A chromatography column,which was performed in accordance with the product instruction.

The ELISA Method:

1. Coating: 0.05M PH 9.0 carbonate coating buffer was used to dilute theantibody (primary antibody: goat anti-human IgG) to a protein content of1˜10 μg/ml. 0.1 ml was added into each reaction well of the polystyreneplate, staying overnight at 4° C. The next day, solutions were discardedform the wells, which were washed three times with a washing buffer,each for three minutes. (Hereinafter, referred to as washing).

2. Sample loading: 0.1 ml diluted sample to be assayed was added intothe above coated reaction well, incubated at 37° C. for 1 h, and thenwashed. (The blank well, positive control well and negative control wellwere set at the same time).

3. Loading of the enzyme labeled antibody (secondary antibody: goatanti-human IgG-HRP (goat anti-human IgG-horseradish peroxidase)): intoeach reaction well, 0.1 ml freshly diluted enzyme-labeled antibody(dilution after titration) was added, incubated at 37° C. for 0.5˜1 h,and then washed.

4. Addition of substrate for color development: into each reaction well,0.1 ml temporarily formulated TMB substrate solution was added, stayingat 37° C. for 10˜30 min.

5. Termination reaction: into each reaction well, 0.05 ml 2M sulfuricacid was added.

6. Result determination: direct observations may be made on a whitebackground with naked eyes: the darker in the reaction well, thestronger the positive degree, and the negative reaction was colorless orvery light, which were denoted by “+” and “−” depending on the depth ofthe color displayed. The OD value also can be measured: the OD value ofeach well was measured, after the blank control well was set to zero, ona ELISA detector at 450 nm (if ABTS is used for color development, thenat 410 nm), which, if 2.1 times greater than the prescribed OD value ofthe negative control, indicates a positive.

The Reagents

(1) Coating buffer (PH 9.6 0.05M carbonate buffer): Na₂CO₃ 1.59 g,NaHCO₃ 2.93 g, and distilled water added to 1000 ml.

(2) Washing buffer (PH 7.4 PBS): 0.15M: KH₂PO₄ 0.2 g, Na₂HPO₄.12H₂O 2.9g, NaCl 8.0 g, KCl 0.2 g, Tween-20 0.05% 0.5 ml, and distilled wateradded to 1000 ml.

(3) Dilution solution: bovine serum albumin (BSA) 0.1 g and washingbuffer to 100 ml; or formulated with serums, such as sheep serum, rabbitserum and the like and the washing buffer into 5˜10% for use.

(4) Stopping Solution (2M H₂SO₄): distilled water 178.3 ml, andconcentrated sulfuric acid (98%) 21.7 ml dropwise added.

Purification of the antibody with the rProtein A chromatography column:purification medium: HiTrap rProtein A FF, 5 ml, Cat. No.: 17-5079-01,purchased from GE Company, referring to the Manual provided by thecompany for detailed instruction for use.

Operations:

1) Cleaning up: 1M NaOH and ddH₂O were sequentially used to clean theconduit, and the small filter was boiled with 0.1M NaOH for 10 min andthen immersed with ddH₂O for 1˜2 min;

2) Setting Program and linking the rProtein A affinity chromatographycolumn;

3) 20 mM binding buffer (pH 7.0) was used to balance the chromatographycolumn;

4) The prepared cell supernatant was loaded at a flow rate of 1˜2ml/min; preparation of the cell supernatant: centrifugating at 12000 gfor 15 min, and removing the supernatant which was then sterilized byfiltering through a 0.22 um nitrocellulose filter film.

5) 1M elution buffer (pH 3.0) was used to elute the target protein whenthe loading was nearing completion;

6) The protein was collected, adjusted to pH 7.0 with Trise base (pH9.0), and detected by electrophoresis;

7) The conduit and small filter were cleaned in accordance with step 1).

Sodium phosphate buffer (binding buffer): used as the binding buffer forProtein A purification. The formulation method was as follows: 1MNa₂HPO₄, 57.7 ml, and 1M NaH₂PO₄, 42.3 ml, were uniformly mixed to give100 ml of 0.1M sodium phosphate buffer, pH 7.0, which was then dilutedto 20 Mm with distilled water for use.

Citric acid/sodium citrate buffer (elution buffer): used as the elutionbuffer for Protein A purification. The formulation method was asfollows: 0.1M citric acid, 186 ml, and 0.1M sodium citrate, 14 ml, wereuniformly mixed to give 200 ml of 0.1M citrate buffer, pH 3.0.

III. Detection of Protein

The goat anti-human IgG-HRP antibody, Cat. No.: (046K4801), waspurchased from Sigma Company; the goat anti-mouse IgG1, Cat. No.:(1010-05), was purchased from SBA (Southern Biotechnology Associates,Inc.);

SDS-PAGE: 15 μl elution buffer (i.e., antibody solution) was subjectedto a reducing SDS-PAGE electrophoresis on 12% gel, and stained withCoomassie brilliant blue R-250.

The results indicate that the heavy chain and the light chain of thepurified antibody have a relative molecular mass of 25×10³ and 50×10³,respectively (FIG. 3 and FIG. 4), which is consistent with the expectedresults. In FIG. 3, lane 2 denotes the present antibody C3, and lane 3denotes the control, i.e., the cetuximab.

Immunobiological imprinting analysis: additional elution buffer wastaken to perform the reducing SDS-PAGE electrophoresis on a 12% gel, andthen transferred to a nitrocellulose membrane, which was sealed at roomtemperature with a membrane blocking solution (1×PBST, comprising 5%skim milk powder) for 2 h, incubated with a goat anti-human IgG-HRPantibody diluted 1:5000 for 2 h (room temperature), and then washed 3times with 1×PBST. Finally, color was developed by using ECL, andexposures were made with X-ray film. This analysis was simultaneouslyperformed on the control added with an anti-murine IgG1. In FIG. 4, lane3 denotes the present antibody C3; lane 2 denotes the murine monoclonalantibody negative control; and lane 4 denotes the positive control,i.e., the cetuximab.

The immunobiological imprinting (12%) analysis demonstrates that theantibody may specifically bind a goat anti-human IgG. However, there aresome non-specific hybridizing bands (including commercial cetuximab)which partially react with the anti-human IgG secondary antibody,possibly due to the mixture with a portion of non full-length heavychain fragments during purification. Nevertheless, the above resultshave no influence on the affinity estimate of the antibodies. The aboveantibodies each does not react with the anti-murine IgG1 antibody.

Since the light chain and heavy chain of the present antibody areproportionately expressed on the same expression vector, theyspontaneously constitute a complete antibody comprising two light chainsand two heavy chains.

EXAMPLE 3 Function Detection of the Antibody

EGFR protein was purchased from (Sigma), Cat. No.: (E2645-500UN).

I. Biacore Assay of Binding Capability Between the Antibody and Antigen

The affinity between antibody C3 and EGFR was determined with aBiacore3000 equipment. 10 mmol/L NaAc with different pH values (4.0,4.5, 5.0 and 5.5) were formulated to dilute the EGFR protein, and afterpreconcentration on a CM5 chip, NaAc with optimum pH value was selectedto dilute the protein. The purified antibody (i.e., the elution bufferresulting from Step II in Example 2) was covalently coupled to a CM5sensing chip, mobile phase: HBS-EP (pH 7.4), flow rate: 20 μl/min. Fivedifferent concentrations of antibody C3 (0, 10.55, 21.1, 42.2 and 84.4nmol/L) were taken for the detection of binding affinity with the EGFRprotein. The affinity was calculated with an attached software ofBiacore300. Meanwhile, the cetuximab was used as a control.

The experiments were conducted in triplicate with the average valuetaken as the result.

The results show that C3 displays a favorable binding activity (with anaffinity of 6.13×10⁻¹⁰ mol/L) to the antigen EGFR. The cetuximab has anaffinity of 1.1×10⁻⁹ M.

II. Tumor Cell Invasion Experiment

The SW480 cell, Cat. No.: (ATCC® Number: CCL-228™), was purchased fromthe American Type Culture Collection (ATCC); the cetuximab antibody waspurchased from Merck KGaA in Germany (original English brand name:ERBITUX; original English drug name: Cetuximab; Chinese translatedreference product name: aibituo (

); molecular structure name: cetuximab; country of origin: Germany;manufacturer: Merck KGaA in Germany).

The SW480 cell was cultivated with a RPMI1640 medium (purchased fromInvitrogen Company, Cat. No.: 31800-022). The invasion chamber washydrated with the serum-free RPMI1640 medium, incubating for 2 h (37°C., 5% CO₂). The serum-free RPMI1640 was removed, and into the porechamber of the invasion chamber (BD BioCoat™ Matrigel™ Invasion Chamber,purchased from BD Company, Cat. No.: 354480), 750 μl RPMI 1640(containing 10% serum) was added; 475 μl RPMI1640 (containing 1% serum)was added into the insert chamber, into which, 25 μl of digested SW480cell (cell number >10⁵/500 μl) was added afterwards, and finally, thenegative control PBS and the present antibody respectively; each samplehas two pores, and the antibody has a final concentration of 100 ng/ml.After a 24 h incubation, cells that cannot penetrate the basic film ofthe invasion cassette were wiped off with a sterile cotton swab; cellspenetrated the basic film were fixed, stained, and dried at roomtemperature prior to count under the optical microscope.

The corresponding cell number was counted under a 100× microscope forthe samples in each insert chamber. Comparing the antibody group and thePBS group by using a Dunnett t3 (bilateral analysis) assay, if P<0.05,the differences between these two treatment effects may be considered tobe statistically significant.

A variance analysis of single factor of four levels was conducted on thecell invasion experimental data by using the SPSS12.0 statisticalsoftware, which shows F_(0.05(3,44))=2.82 and P<0.05, indicating thatthe cell numbers are not equal or not completely equal.

The results of Dunnett t3 (bilateral analysis, hereafter referred to ast) assay (Table 1) demonstrate that the t value of PBS group and C3group is 3.43, and P is less than 0.01, indicating that the anti EGFRantibody C3 has certain inhibition to the invasion of SW480 tumor cell.

TABLE 1 the results of Dunnett's t3 assay for the cell invasionexperiment Groups n average number of cells PBS group 12 86 ± 16.222 C3group 12  56 ± 5.0416** Note: comparing with the PBS group, **P = 0.003,**t = 3.43.

INDUSTRIAL APPLICATION

The antibody of the present invention has a good binding activity (withan affinity of 6.13×10⁻¹⁰ M) and an ability of inhibiting tumor cellgrowth and migration; however, the anti-EGFR human-murine chimericantibody, cetuximab, commonly found in foreign market has an affinity of1.1×10⁻⁹ M. The present humanized antibody is capable of better bindingwith EGFR, thus guaranteeing the anti-tumor effect thereof. The presentmethod for preparing an antibody enables the light chain and the heavychain to be expressed simultaneously, such that the expression ratio ofthe light chain to the heavy chain gets closer to 1:1, producing ahigher ratio of matching double strand antibodies. In summary, theantibody and preparation method thereof of the present invention willhave a broad application prospect in the field in preventing and/ortreating a tumor.

What is claimed is:
 1. An antibody, wherein the heavy chain variableregion of the antibody has the amino acid sequence as set forth by SEQID NO. 3, and the light chain of the antibody has the amino acidsequence as set forth by SEQ ID NO.
 2. 2. The antibody according toclaim 1, wherein the antibody comprises a heavy chain and the lightchain, and the heavy chain comprises the heavy chain variable region anda heavy chain constant region.
 3. The antibody according to claim 2,wherein the heavy chain constant region comprises an amino acid sequenceas set forth by SEQ ID NO.
 11. 4. An inhibitor for inhibiting (1) asignal transduction pathway of epidermal growth factor receptor or (2) acolon cancer cell invasion, wherein an active ingredient of theinhibitor is the antibody of claim
 1. 5. The inhibitor according toclaim 4, wherein the colon cancer cell is a SW480 cell.
 6. A drug fortreating colon cancer, wherein an active ingredient of the drug is theantibody of claim
 1. 7. The drug according claim 6, wherein the tumorcell is a SW480 cell.
 8. A method for inhibiting signal transductionpathway of epidermal growth factor receptor comprising preparing aninhibitor of the antibody of claim 1 and administering the inhibitor inan effective amount.
 9. A method for inhibiting a colon cancer cellinvasion comprising preparing an inhibitor of the antibody of claim 1and administering the inhibitor in an effective amount.
 10. The methodaccording to claim 9, wherein the tumor cell is a SW480 cell.
 11. Amethod for treating colon cancer comprising preparing a drug comprisingthe antibody of claim 1 and administering the drug in an effectiveamount.
 12. The method according to claim 11, wherein the colon cancercell is a SW480 cell.
 13. A method of inhibiting signal transductionpathway of epidermal growth factor receptor comprising administering theantibody of claim 1 in an effective amount to an individual in needthereof.
 14. A method of inhibiting a colon cancer cell invasioncomprising administering the antibody of claim 1 in an effective amountto an individual in need thereof.
 15. The method according to claim 14,wherein the tumor cell is a SW480 cell.
 16. A method of treating a coloncancer comprising administering the antibody of claim 1 in an effectiveamount to an individual in need thereof.
 17. The method according toclaim 16, wherein the colon cancer is a SW480 cell.